(CNN) -- Based on early returns, CNN projects that Democrat Travis Childers defeated Republican Greg Davis in a Tuesday special election for an open congressional seat in northern Mississippi.

For Democrats, the decisive victory by Childers is the latest in a series of special-election wins for the party and provides a strong tailwind heading into the November elections. Republicans had held the seat since 1994.

For Republicans, Davis' defeat is viewed as a possible preview for a widespread GOP thrashing in November, and it shows that trying to link local Democrats in conservative districts to Sen. Barack Obama and his former pastor was not a winning strategy.

Childers and Davis, the mayor of Southaven, Mississippi, faced off in the special election to fill the state's 1st congressional district seat vacated by former Rep. Roger Wicker. He left the seat late last year after Mississippi Gov. Haley Barbour tapped him to replace Trent Lott in the Senate.

Lott, the onetime Senate Majority Leader, retired in December to become a lobbyist.

The two candidates had faced off in an April 22 election that featured several other minor candidates. Childers also won that vote over Davis, 49 percent to 46 percent. But a second vote was forced because neither candidate got more than 50 percent of the ballots.

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The election only determines who fills the seat until the end of the year, though its ramifications could be much broader. The district, which includes the northwest part of the state, has been a reliably Republican one. Wicker easily held the seat for 13 years, and President Bush carried the district in 2004 by more than 60 percent.Watch how Childers' win impacts presidential race »

The Republican Party used the election as a key testing ground for a strategy that's expected to be deployed in several districts next fall. The National Republican Congressional Committee, the conservative group Freedom Watch and Davis himself reportedly spent close $1 million airing television commercials that linked Childers to Obama.

The district includes Columbus; some of the Memphis, Tennessee, suburbs; Elvis Presley's birthplace of Tupelo; and Oxford, home of the University of Mississippi. Vice President Dick Cheney stumped for Davis on Monday.

Democrats poured $1 million into the Mississippi district, hoping a win there would lead to a third Republican defeat in as many months and provide a boost of momentum ahead of this fall's congressional races, in which Democrats hope at least 50 Republican seats are in play.

While Childers attacked Davis for supporting trade deals the Democrat blamed for costing Mississippi jobs and for raising taxes as fees as mayor, the National Republican Congressional Committee sponsored a television ad tying Childers to Obama and the Democrats' 2004 presidential nominee, Sen. John Kerry of Massachusetts.

In the ad, Childers is shown next to Kerry and Obama while the Illinois senator's ranking from the National Journal as the most liberal senator is noted. Read more on the ad controversy

In an ad paid for by Davis, the Rev. Jeremiah Wright is shown and a narrator chastises Childers for not publicly denouncing the pastor's controversial remarks. That ad also claimed Obama had endorsed Childers. Watch how Obama's former pastor may cost him »

Childers immediately rejected the notion that Obama had endorsed his candidacy, a sign that even some Democrats may be worried about being too closely associated to the frontrunner in the race for the Democratic nomination.

"Sen. Obama hasn't endorsed my candidacy," Childers said after the ad began to air. "I have not been in contact with his campaign, nor has he been in contact with mine."

The NRCC later said those comments "not only [said] a lot about himself, but also about the toxicity an Obama candidacy can bring to Democratic campaigns down-ballot."

Recently, Republicans failed to win a Louisiana congressional race by using similar tactics. The GOP ran an ad there linking Democrat Don Cazayoux to Obama and House Speaker Nancy Pelosi, but Cazayoux won the May 3 election by three percentage points. The Baton Rouge-area district hadn't sent a Democrat to Washington since the 1970s.

In March, Democrat Bill Foster won a special election victory in former House Speaker Dennis Hastert's Illinois district, another Republican stronghold.